Tremolant mechanism



Feb. 10, 1970 J. A. KOEHL 3,495,022

TREMOLANT MECHANISM Filed Nov. 14'. 1966 :s Sheets-Sheet 2 INVENTOR.

Feb. 10, 1970 J. A. KOEHL 3,495,022

TREMOLANT MECHANISM Filed Ndir. 14, 1966 3 Sheets-Sheet 3 United States Patent 3,495,022 TREMOLANT MECHANISM James A. Koehl, Los Angeles, Calif., assignor to Chicago Musical Instrument Company, Lincolnwood, Ill., a corporation of Delaware Filed Nov. 14, 1966, Ser. No. 599,338 Int. Cl. GlOh 1/04 US. Cl. 84-1.25 5 Claims ABSTRACT OF THE DISCLOSURE This invention relates generally to electrical musical instruments and particularly to electric and electronic organs employing rotary means operating on Dopplers principle to modulate sound of constant musical frequency and desired timbre as a function of orbital travel thereof at a relatively high angular velocity about an axis with resulting cyclic change in both amplitude and apparent frequency thereof at a given vibrato rate and continuing changing phase relations of the partial components of said sound to secure celeste, chorus, ensemble and similar massed sound effects for enhancement of music.

The vibrato is a frequency modulation of a musical tone accompanied by an amplitude modulation at the modulating frequency as well as a pulsating change in timbre.

The chorus is an effect on the human hearing mechanism where several instruments of the same kind are playing in unison and there exists a slight difference between two nominally similar tones and continuing changing phase relations thereof as in the familiar case of several violins playing in unison where the vibrato rates are different and the mean frequencies and the harmonic partial frequencies are also different.

The celeste is an organ stop designating wavering or tremulous tones, or beats, because of slight differences in pitch between its sets of pipes or between its single set and that of another stop with which it is sounded, such as the gamba celeste or the vox celeste.

According to Dopplers principle, if the distance is changing between the observer and a source of constant vibrations, the wave number appears to be greater or less than the true value, according as distance is diminished or lengthened.

Advantage has been taken of the Doppler phenomenon in the field of electrical musical instruments to impose vibrato per so on electrically produced music. This has been accomplished by delivering a sound of constant musical frequency to a sound emitting channel and rotating the channel at a constant angular velocity about an axis with resulting orbital travel of emitted sound about said axis and cyclic change in both amplitude and apparent frequency thereof at a given vibrato rate. As distinguished from single channel devices of the prior art, Kannenberg, in his U.S. Patent No. 2,287,105, for electronic organ, employs means operating on Dopplers principle to produce celeste and choir effects. He accomplishes this by dividing the output tone signal energy of an audio power amplifier among respective equiangularly space dapart directional loudspeakers rotating about a common axis at a constant angular velocity with resulting orbital travel about said axis of sounds emitted by each separate loudspeaker and cyclic change in both amplitude and apparent frequency thereof at a vibrato rate and mixing the respective modulated sounds in the air to secure the aforementioned celeste and choir effects.

The basic concept of the herein disclosed invention finds expression in structurally and functionally new and novel acoustic transducer means operating on Dopplers principle for causing the total sound of constant musical frequency delivered thereto from a stationary loudspeaker to divide into separate portions each of the same partial composition as said delivered sound and for modulating each of said portions at a vibrato rate as a result of orbital travel thereof about an axis at a constant angular velocity and causing the respective modulated portions to be combined in the air to obtain celeste, chorus, ensemble and similar massed sound effects for enhancement of music.

Other objects and advantages are:

The provision of a system for producing massed sound effects which is devoid of electrical and mechanical complications inherent in prior systems and is exceedingly simple, reliable in operation and can be economically manufactured and is relatively of light weight and compact as compared with prior systems requiring rotation of loud speakers with particular reference to the type of system disclosed in the aforementioned Kannenberg Patent No. 2,287,105.

The provision of a system of the class and for the purpose shown and described in which the herein disclosed rotary acoustic transducer may be made of wood or other suitable well known material or manufactured by any conventional molding process using synthetic plastic compositions.

The provision of a system embodying an unique form of rotary acoustic transducer in which directional sound emitters are symmetrically arranged and the weight equally distributed to insure smoothness in operation and prevention of strains, loads and stresses on the motion imparting system for rotating the transducer at a constant angular velocity.

The provision of a system for producing chorus and similar massed sound effects which may be conveniently incorporated in the signal transmission system of any electrical musical instrument.

The invention consists substantially in the construction, combination, location and relationship of parts and the method in connection therewith, all as will be more fully hereinafter set forth; as shown by the accompanying drawings and finally pointed out in the appended claims.

FIGURE 1 is a view in elevation of one exemplified form of the invention.

FIGURE 2 is a vertical section of the form of the invention shown in FIGURE 1 with parts shown in full lines and parts broken away.

FIGURE 3 is a view in transverse section taken on line 33 of FIGURE 2.

FIGURE 4 is a view in transverse section taken on line 4-4 of FIGURE 2 and looking in the direction of the arrow.

FIGURE 5 is a view in transverse section taken on line 55 of FIGURE 2 looking in the direction of the arrow.

FIGURE 6 is a view in side elevation of another exemplified embodiment of the invention schematically showing the invention connected in a conventional tone signal transmission system.

FIGURE 7 is a transverse section taken on line 77 of FIGURE 6.

FIGURE 8 is a vertical section taken approximately on line 8-8 of FIGURE 7 with parts eliminated, and

FIGURE 9 is a schematic view of a still further exemplified embodiment of the invention.

Referring to FIGURES 1 and 2, the substantially cylindrical acoustic transducer 10 comprises end members 19' and 21 and an intermediate member 20, each of circular shape and of the same diameter.

Member 19 shown in detail in FIGURE 3 is a rigid body having a central hub portion 22 from which solid dividing walls 26 radiate and are spaced 120 apart from each. other, the outer extremities of said walls being spaced the same radial distance from the perimeter of the member. Preferably formed integral with the body portion of the member and continuing into the outer extremities of the respective walls 26 are arcuate walls 27 arranged eccentric to the axial center of hub portion 22, and as shown, the outer extremity of each of said walls is disposed substantially on a line radial to said axial center and spaced apart from the outer extremity of the next succeeding dividing wall 26 to provide therewith a sound emitting mouth M. The arrangement is such that the dividing walls 26, the solid portion of member 19 and the respective arcuate walls 27 mutually define scooplike directional sound emitters A, B and C, each of which is closed at one side by the body portion of said member and open at its opposite side. It is noted that the Mouths M are also spaced 120 apart from each other and disposed substantially tangential to the perimeter of member 19 and arranged facing in a clockwise direction about said axial center as indicated by arrow (a). Upon referring to FIGURE 2, it is observed that the face width of the walls 27 is the same as the dividing walls 26 taken in a plane parallel to said axial center and that the edges of the walls 26 and 27 are flush with each other.

Member 20 shown in FIGURE 4 is generally the same as member 19 except that the dividing walls 26a of hub portion 22a, when combined with surfaces of the body portion of said member and the arcuate walls 27a, define equiangularly spaced apart scoop-like sound emitters D, E and F, the mouths M1 of which are arrange-d facing in a counter clockwise direction. Another difference is that the body portion of said member has openings between the dividing walls 26a and concentric to the axial center of the member so that the emitters D, E and F are substantially completely open at both sides.

Member 21 shown in FIGURE 5 is plane surfaced at both sides and has a hub portion 22b with radial spokes 21a respectively providing openings 01 therebetween and concentric to the axial center of said member, said openings being dimensionally the same as the openings 0 in member 20.

As shown in FIGURE 2, members 19, 20 and 21 have their hub portions 22, 22a and 22b in axial abutment with each other and may be secured in this condition by any obvious means, preferably an adhesive composition. The free edges of the arcuate walls 27 of member 19 abut flat confronting surfaces of the body portion of member 20 laterally of the openings 0 therein. Similarly, the free edges E1 of the arcuate walls 27a: a member 20, laterally of openings 01 therein abut the confronting fiat surface of the body portion of member 21. Assembled and firmly secured together, transducer is completely closed at one end by member 19 and substantially completely open :at its opposite end. The transducer is s pported by a shaft 23 mounted at one end in a bearing S in a stationary support 11, the opposite end being similarly mounted in a bearing S1 in a stationary flat baffle 12 disposed parallel to said support 11. The baffle has a circular series of openings 02 of the same dimensional size as openings 0 and O1 in said members and 21 so that all of said openings 0, O1 and O2 establish intercommunication between the directional sound emitters A, B, C, D, E and F, whereby sound delivered to the transducer via openings 02 will be divided among said emitters. Mounted in the baflle 12 is a direct radiator loudspeaker 13 of the conical diaphragm type, arranged with the front of the cone 14 facing openings 02 in said baffle. The diameter of the rim of the cone is approximately equal to that of a circle I describing the boundry of said openings 02. Mounted on the transducer member 19 is a driven pulley 15, and as shown in FIGURE 1 said pulley is connected by a belt 16 (illustrated by dotand dash lines) .to-a pulley 17 on the shaft 17 of a constant speed electric motor 18 mounted on support 11. The ratios of the pulleys 15 and 17 are mathematically calculated to secure rotation of the transducer at a given constant angular velocity with resulting orbital travel of emitted sound about the axis of rotation of the transducer at a vibrato rate of the order of from 5 to 8 c.p.s.

From the above description of the structural features of the preferred embodiment of the invention, transducer 10 is characterized by a first set of sound emitters A, B and C, with mouths M facing of which face in a clockwise direction and disjointly related about the axis of rotation of the transducer, and a second set of sound emitters D, E and F with mouths M1 facing in a counter clockwise direction and disjointly related about said axis. Mouths A, B and C and mouths D, E and F are equiangularly spaced 60 apart in relative alternation with mouths M1 in trailing relation to mouths M. While the direction of rotation of the transducer is given as clockwise, the herein referred to functional result is the same regardless of the direction of rotation.

Assuming that the direction of rotation of the trans ducer is clockwise as indicated by arrow (a) in FIG- URE 3, sounds emitted by mouths M will cyclically vary both in amplitude and apparent frequency. As the mouths approach an observer the apparent pitch is higher and the amplitude relatively high, the amplitude and pitch being lower as mouths M recede from the observer. The same effect is had with emission of sounds from mouths M1 facing in the counter clockwise direction except that the effect is the reverse, the amplitude being greater as mouths M1 recede from the observer.

Particular stress attaching to the feature of the invention consisting in dividing sound of constant musical'frequency and desired timbre into separate portions of the same partial composition as the output sound as it continuously originates at sound source 13 and vibrato modulating each separate portion of the sound and combining the modulated portions in the air to produce massed sound effects. To the best of my knowledge, this basic feature, as compared with systems of the prior art, has never before been proposed, suggested or contemplated by others. Massed sound effects, Whether broad or narrow are, of course, proportional to the number of portions into which sound of constant musical frequency is divided and each portion vibrato modulated to obtain rapid cyclic change in phase relations of the fundamental and upper harmonic frequencies of nominally similar tones accompanied by continuing change in both amplitude and apparent frequency of said portions.

Referring to FIGURES 6, 7 and 8, the transducer 28 is a cylindrical body consisting of a closed end 29 and an end 30 having openings 31 encircling a central hub 32 and an intermediate member 33 of ogee configuration. in transverse section providing sound emitters 3434 having mouths 35 equiangularly spaced apart from each other and arranged facing in the same direction about about the axis of rotation of the transducer. .A shaft 36 supports the transducer for rotation in a frame 37 or equivalent thereof, the same being open at all sides for discharge to the air of sound as it is delivered to said emitters 34 via said openings 31. The source of sound comprises a direct radiator loudspeaker 38 of the conical diaphragm type mounted in a flat baffle 39 of said frame 37 and arranged to radiate sound to said emitters via opening 04 in said baflle.

Shown in block diagram in FIGURE 6 is an electric organ 40 of any well known type having a timbre control system adapted to receive toneisignals of constant musical frequency from tone generators and deliver same to an audio amplifying system 41 from which the output thereof is fed to loudspeaker 38. As shown, the amplifying'system includes a volume control device 42.

The transducer supporting shaft 36 may be operated by any well known variable speed electric motor 36a enabling rotation of the transducer at any selected constant angular velocity to cause sound discharged to the air from the mouths of emitters 34 to travel an orbital path about the axis of rotation of the transducer to impose vibrato on the emitted sounds as a function of rotation of the transducer at the selected angular velocity. In this embodiment of the invention the modus operandi is the same as the embodiment shown at FIGURES l-S, the difference being in the number of and arrangement of sound emitters employed to obtain a given mass effect. That is to say, the effect on the human mechanism of hearing of a narrow massed effect as compared to a relatively broad effect using the embodiment of the invention shown in FIGURES 1-5, inclusive.

Referring to the embodiment shown in FIGURE 9, the acoustic transducer a may be like transducer 10 or transducer 28. In FIGURE 9 the baflie 43 supports a flared sound spreader 44 aligned with openings 45 in said baffle. Mounted in the baflle is the driver 47a of a horn loudspeaker, the throat of which opens to the sound spreader at the small end thereof so that sound origination at the driver will be delivered to the transducer via said openings 45 and divided between the emitters of the transducer.

The sound emitters shown in each embodiment of the invention have large throats, which in either embodiment, is encompassed by a circle concentric to the axis ofrotation of the transducer and would be approximately the same at the diameter of the rim of the cone of the loudspeaker 13 shown at FIGURES 1-6, inclusive, or the large end of the spreader 44 shown at FIGURE 9. The mouths M and M1 extend in a plane parallel to the axis of rotation of the transducer and are small compared with the throats.

It is common practice to embody in the sound reproducing system of electric and electronic organs separate amplifiers and associated loudspeakers for the manuals and pedal organ, each loudspeaker having a frequency range different from that of the others so as to prevent dissonance caused by intermodulation of the upper partial frequencies by heavy pedal note frequencies which would occur at high volume levels. It is also common practice to modulate frequencies for a range covering the middle and upper registers of the instruments gamut, and it has proved advisable to omit vibrato on bass note tones or, instead, to impose light amplitude modulation on bass note tones. The same care is taken with other sound reproducing systems such as Stereophonic systems.

Referring again to FIGURE 2 wherein sound emitters A, B and C and D, E and F, jointly contribute to the production of a broad massed effect, a narrow effect can be secured simply by using in the fabricating process members 19 and 21, the former providing one side and the latter, the other side, with emitters A, B and C disposed between said sides with their open sides facing openings 01 in member 21.

Regarding cyclic change in both amplitude and apparent frequency and rapid phase shift between the components of respective sounds, it is, of course, necessary that at least two sound emitters be used to secure a massed sound effect as distinguished from straight forward frequency modulation at a vibrato rate imposed on the total sound emitted by a single channel and in orbital motion about an axis. In the embodiment shown in FIG- URE 8 where the emitter mouths 35 are diametrically related, two different Doppler effects continuously occur (1), the approach of sound relative to a point of observation and (2), recession of the sound. When, as distinguished from emitters 35 spaced 180 apart from each other, the number of emitters is increased by a multiple of two as in the embodiment shown in FIGURES 1 to 5 inclusive, two different Doppler effects are obtained in rapid alternation. When two emitters are employed as when the transducer comprises only the members 19 and 21, the two Doppler effects are obtained in rapid alternation. I have shown several embodiments of the inventions, each having a different number of sound emitters, it being apparent to persons ordinarily skilled in the art that the number of emitters can be increased without departing from the spirit and intention of the invention.

What I claim is:

1. Tremolant mechanism comprising, a source of sound of constant musical frequency and selected timbre, a cylindrical acoustic transducer rotatable about an axis and having at least two directional sound emitters, each characterized by interrelated walls having form and shape in a plane transversely of said axis providing mouths equiangularly related about the perimeter of said transducer and throats that are large relative to said mouths and communicate with said source to receive respective portions of the output thereof and effect emission of said portions from said mouths, and means for rotating the transducer unidirectionally at a constant angular velocity to cause tremolant modulation and mixing together the emitted portions to obtain a musical sound effect consisting of only the frequencies of said modulated portions of said output.

2. Tremolant mechanism according to claim 1 wherein a substantial portion of each of the walls describes an arc of a circle excentric to said axis.

3. Tremolant mechanism according to claim 1 wherein a substantial portion of each of said walls describes an arc of a circle concentric with said axis.

4. Tremolant mechanism comprising, a source of sound of constant musical frequency and selected timbre comprising an acoustic transducer rotatable about an axis and having at least two sets of directional sound emitters with throats communicating with said source to receive respective portions of the output thereof and mouths equiangularly and disjointly related about said axis, and wherein the mouths of said sets respectively face clockwise and counter clockwise about said axis and are alternately related, and means for unidirectionally rotating said transducer at a given constant angular velocity to cause orbital travel of the emitted portions of said output about said axis and secure tremolant modulation and mixing together thereof in the air.

5. Tremolant mechanism comprising, a source of sound of constant musical frequency and selected timbre, an acoustic transducer rotatable about an axis and consisting of coaxial members, each having directional sound emitters with mouths equiangularly related about said axis and throats communicating with said source to receive respective portions of the output of said source and effect emission thereof from said mouths, and wherein, the mouths of said emitters of the respective members respectively face clockwise and counter clockwise about said axis in relative alternation, and means for rotating the transducer unidirectionally at a constant angular velocity to cause orbital travel of the respective emitted portions of said output about said axis with resulting tremolant modulation and mixing together thereof in the air.

References Cited UNITED STATES PATENTS 2,869,669 1/1959 Leslie 841.25 X 3,095,467 6/1963 Schwartz et a1. 84-125 3,192,322 6/1965 Leslie 841.2S X

HERMAN KARL SAALBACH, Primary Examiner SAXFIELD CHATMON, IR., Assistant Examiner U.S. Cl. X.R. 181-27, 33 

